The present invention relates to a liquid surface heating arrangement for heating the floors, which arrangement includes a plurality of tubes laid in primary layer of the floor in a meander-shaped or bifilar manner and disposed in passages formed in prefabricated elements of heat-isolating material, which form that primary layer.
A liquid surface heating arrangement of the type under consideration is disclosed in applicant's German patent No. 2,248,228. With this known arrangement heat is transmitted to the floor from heating tubes via a heat-conducting metal sheet onto which a floor finish is additionally applied. The known constructions are, however highly expensive and it has been desired to reduce costs of floor heating.
It has been suggested to lay heating tubes of synthetic plastic immediately into the floor finish, without heat-conducting metal sheet. This, however, caused considerable problems during the laying the tubes down and also after the completion of the floor heating.
It has been known that heating tubes are normally arranged in clamping holders formed of various materials, distributed in spaced relationship from each other over the heatisolating primary layer of the floor so that the heating tubes are entirely enclosed with a coating of the floor finish. This, however, means that the heating tubes, after being laid on the primary layer and secured in clamping holders, lie freely over the heat-isolating layer which must be used as a walkway by workers. It has been therefore inevitable that the installed heating tubes would be displaced to the side or bent or shifted from the clamps by workers with the result that the required uniform spacing between the heating tubes would no longer be maintained and this would effect the temperatures in the floor finish layer. Cracks can be formed in the finish layer in a short period of time, which cracks would extend from the upper surface of the finish layer up to the heating tubes. Because of the danger of the formation of cracks in the finish layer due to heat fluctuations which may occur in the heating tubes the middle thickness of the finish layer above the heating tubes must be about 45 mm (according to the instructions of Central Federation of the German Building Trade Committee). If the heating tubes can be forcefully lifted from the floor primary layer this means that the finish layer must have the thickness which is greater than that of the usually utilized floor finish. The finish layer with an additional mass however, makes the floor layer usually worse in regard to desired heat transmission from the heating tubes to the upper side of the floor.